I'm reading verse 13 again today. It served as a conclusion to the previous parable, but also it introduces the next section - the controversy with the pharisees over money.
Luke lets his careful objectivity slip for a moment, and says something rude about the pharisees. He calls them "lovers of money." So he's clearly siding with Jesus, who has just warned them that they cannot sit on the fence - either they love God, or they love money. It's as stark as that.
For Jesus, the pharisees, though looking righteous, are actually poison. They are doing dreadful harm by kidding people that being like them is what God wants, and when people copy them, they find themselves further from God than they were before. What a travesty! The "godly" are the ones doing the devil's job, tempting people away from God!
Jesus tackles one of their arguments against him, that he is ignoring the law, and letting riff raff in to God's kingdom. No - I'm not ignoring the law, you are! You're so busy finding clever little ways to get round the spirit of the law while obeying the letter of it - divorce being an example - that you completely miss the point.
Divorce had been made easy, so long as it was regularised. Get the paperwork in order, and essentially you could please yourself. That's the way the pharisees played it. Jesus' reply is simple: adultery is adultery, it doesn't matter what you call it. Anyone who has been tempted to break their marriage vows (and show me a person who says they haven't been tempted and I'll show you a liar) will be familiar with the convoluted thought processes that we use to justify it to ourselves. "Of course, in any other circumstance this would be wrong, but ..."
So am I saying that al divorce everywhere is wrong? No. I'm saying don't think legalistically about the law. Jesus didn't. He thought idealistically about it. What is the ideal that the law is trying to uphold?
Honour the ideal, don't just keep the rules.